飞机涡轮风扇发动机市场 - 全球产业规模、份额、趋势、机会、预测：按涡轮风扇发动机、飞机类型、应用、地区和竞争格局划分，2021-2031年

全球飞机涡轮扇发动机市场预计将从 2025 年的 32.8 亿美元成长到 2031 年的 47.1 亿美元，复合年增长率为 6.21%。

该产业专注于吸气式喷射推进系统的製造和分销，该系统利用燃气发生器核心和大型前置风扇，透过空气加速产生推力。市场成长的主要驱动力是：为因应全球日益增长的客运量，对新型民航机的需求不断增加；以及航空公司为替换老旧飞机而需要更节能的机型。此外，军用航空领域的支出增加以及公务航空领域需求的成长，也持续推动对这些高涵道比推进系统的需求。

儘管成长前景强劲，但由于持续的供应链中断，导致原材料采购和零件製造延误，航空业面临严峻挑战。随着需求復苏，引擎製造商面临扩大生产的巨大压力，这些生产瓶颈问题尤其严重。国际航空运输协会（IATA）预测，2024年全球客运量将年增10.4%。客座率的强劲復苏凸显了航空业克服物流瓶颈以满足航空公司运力需求的紧迫性。

市场驱动因素

全球商业航空客运量的成长是涡轮扇发动机市场的主要驱动力，迫使航空公司透过大规模订购新飞机来增强其运力。随着主要地区的旅行需求復苏并超过疫情前水平，航空公司正积极引进窄体和宽体飞机，这直接推动了所需推进系统的生产速度。这一激增不仅促进了新发动机的推出，也带动了现有飞机维护和备件的售后市场发展。根据波音公司于2024年7月发布的《2024-2043年民航机市场展望》，预计未来20年航空业将需要约44,000架新民航机才能满足这项持续​​的需求。因此，主要製造商正在加快生产线运作，以满足庞大的订单积压。

同时，老旧飞机正迅速被新一代节能引擎技术所取代，这正在改变市场动态。排放气体和噪音环境法规迫使营运商退役老旧飞机，转而使用配备高涵道比涡轮扇发动机的飞机，这些发动机具有更高的燃油效率和更低的运营成本。正如空中巴士在2024年7月发布的《2024-2043年全球市场预测》中所指出的，约42%的新飞机交付旨在取代老旧低效的飞机，这是航空业脱碳努力的一部分。这一现代化趋势在主要引擎製造商的财务表现中得到了清晰的体现。根据通用电气航空航太公司在2024年10月发布的《2024年第三季财务业绩订单》，总订单增长28%至126亿美元，凸显了新设备和服务业务的强劲商业性势头。

市场挑战

持续的供应链中断是全球飞机涡轮扇发动机市场扩张的主要障碍。製造商在采购高等级钛和镍等关键原料方面面临严重延误，同时引擎组装所需的专用铸件和锻造件也出现短缺。这些物流障碍迫使原始设备製造商 (OEM) 放慢生产速度，使其无法充分利用航空公司订单的激增。因此，推进装置的完成和运输延误阻碍了飞机的最终交付，使得将市场需求有效转化为利润变得困难。

近期产业指标显示，生产目标与实际产量之间的差距日益扩大，凸显了这些限制因素的严重性。根据国际航空运输协会（IATA）统计，2024年全球民航机订单达到约17,000架的历史新高，但由于生产限制，实际交付最初的年度预测低了约30%。这一显着的交付缺口清楚地表明，儘管需求环境良好，但供应链的脆弱性正直接阻碍市场的实际扩张，导致很大一部分潜在市场价值未能开发。

市场趋势

向超高涵道比 (UHBR) 引擎设计的转变代表着一种旨在最大限度提高推进效率的结构演进。製造商正透过采用齿轮箱来推进风扇转速与低压涡轮的分离。这使得更大的风扇直径和超过 15:1 的涵道比成为可能。这种结构方法透过保持较低的风扇转速，同时使涡轮以最佳转速运作，从而降低燃油消耗。正如《飞行世界》2025 年 10 月号报导的「普惠公司 GTF Advantage 发动机获得欧洲认证」一文中所述，这款先进的 UHBR 发动机旨在使海平面机场的起飞推力提高 4%，高海拔机场的起飞推力提高 8%，凸显了齿轮传动结构的性能优势。

同时，开放式风扇概念的復兴旨在显着降低排放。与传统的涵道式涡轮扇发动机不同，这些结构取消了短舱，实现了现有发动机两倍的涵道比，从而大幅节省燃料。各联盟正积极推动这些设计进入硬检验阶段，并验证其气动稳定性。根据CFM国际公司于2025年7月发布的“关于CFM RISE计划的五点说明”，该合资企业已完成超过250项测试，包括风洞试验，并正致力于改进开放式风扇结构，以适应未来的营运需求。

目录

第一章概述

第二章：调查方法

第三章执行摘要

第四章：客户心声

第五章：全球飞机涡轮风扇发动机市场展望

• 市场规模及预测
  • 按金额
• 市占率及预测
  • 涡轮扇发动机（PW1000、F414、V2500、PW4000、CFM56、CFM LeapX、GP7000、GEnx、Trent 1000、F135）
  • 飞机类型（宽体机、窄体、其他）
  • 依应用领域（军用航空、民用航空运输）
  • 按地区
  • 按公司（2025 年）
• 市场地图

第六章：北美飞机涡轮风扇发动机市场展望

• 市场规模及预测
• 市占率及预测
• 北美洲：国别分析
  • 我们
  • 加拿大
  • 墨西哥

第七章：欧洲飞机涡轮风扇发动机市场展望

• 市场规模及预测
• 市占率及预测
• 欧洲：国别分析
  • 德国
  • 法国
  • 英国
  • 义大利
  • 西班牙

第八章：亚太地区飞机涡轮风扇发动机市场展望

• 市场规模及预测
• 市占率及预测
• 亚太地区：国别分析
  • 中国
  • 印度
  • 日本
  • 韩国
  • 澳洲

第九章：中东和非洲飞机涡轮风扇发动机市场展望

• 市场规模及预测
• 市占率及预测
• 中东与非洲：国别分析
  • 沙乌地阿拉伯
  • 阿拉伯聯合大公国
  • 南非

第十章：南美洲飞机涡轮风扇发动机市场展望

• 市场规模及预测
• 市占率及预测
• 南美洲：国别分析
  • 巴西
  • 哥伦比亚
  • 阿根廷

第十一章 市场动态

• 促进因素
• 任务

第十二章 市场趋势与发展

• 併购
• 产品发布
• 近期趋势

第十三章：全球飞机涡轮风扇引擎市场：SWOT分析

第十四章：波特五力分析

• 产业竞争
• 新进入者的潜力
• 供应商的议价能力
• 顾客权力
• 替代品的威胁

第十五章 竞争格局

• RTX Corporation
• General Electric Company
• Rolls-Royce plc
• MTU Aero Engines AG
• Honeywell International Inc.
• Eurojet Turbo GmbH
• Safran SA
• IHI Corporation

第十六章 策略建议

第十七章：关于研究公司及免责声明

The Global Aircraft Turbofan Engine Market is projected to expand from USD 3.28 Billion in 2025 to USD 4.71 Billion by 2031, registering a CAGR of 6.21%. This sector focuses on the manufacturing and distribution of airbreathing jet propulsion mechanisms, which rely on a gas generator core and a substantial front fan to generate thrust through air acceleration. The market's growth is largely propelled by the escalating requirement for new commercial aircraft to handle increasing global passenger numbers and the operational imperative for airlines to substitute aging fleets with more fuel-efficient options. Furthermore, rising expenditures in military aviation and increasing needs within the business aviation sector continue to strengthen the demand for these high-bypass propulsion systems.

Despite this favorable growth outlook, the industry is grappling with major hurdles due to ongoing supply chain interruptions, which have delayed raw material acquisition and component fabrication. These production bottlenecks are especially problematic as rebounding demand exerts immense pressure on engine manufacturers to hasten their output. According to the International Air Transport Association (IATA), total full-year global passenger traffic increased by 10.4% in 2024 compared to the prior year. This strong recovery in utilization highlights the critical need for the sector to overcome logistical limitations to satisfy the capacity requirements of airlines.

Market Driver

Increasing global commercial air passenger traffic acts as the central force behind the turbofan engine market, pushing airlines to bolster their capacity through substantial orders for new aircraft. As travel demand rebounds and surpasses pre-pandemic benchmarks in key regions, carriers are actively acquiring narrow-body and wide-body jets, which directly elevates production rates for the necessary propulsion systems. This surge drives not only the installation of new engines but also the aftermarket sector for maintenance and spare parts to maintain existing fleet operations. According to Boeing's 'Commercial Market Outlook 2024-2043' published in July 2024, the aviation industry is anticipated to need nearly 44,000 new commercial airplanes over the next 20 years to satisfy this enduring demand, causing original equipment manufacturers to accelerate assembly line activity to meet the significant backlog.

Simultaneously, the rapid substitution of aging fleets with fuel-efficient, next-generation engine technologies is altering market dynamics. Stringent environmental regulations concerning emissions and noise are compelling operators to retire older aircraft in favor of models fitted with high-bypass ratio turbofans, which deliver superior specific fuel consumption and lower operating expenses. As noted in Airbus's 'Global Market Forecast 2024-2043' from July 2024, roughly 42% of anticipated new aircraft deliveries are designated to replace older, less efficient units to aid industry decarbonization efforts. This modernization trend is evident in the financial results of leading engine makers; according to GE Aerospace's 'Third Quarter 2024 Financial Results' released in October 2024, total orders rose by 28% to USD 12.6 billion, highlighting the strong commercial momentum for both new equipment and services.

Market Challenge

Ongoing supply chain disruptions stand as the primary barrier hindering the expansion of the Global Aircraft Turbofan Engine Market. Manufacturers face acute delays in obtaining essential raw materials, such as high-grade titanium and nickel, along with a shortage of specialized castings and forgings required for engine assembly. These logistical obstructions compel Original Equipment Manufacturers to slow down production speeds, preventing them from fully leveraging the current influx of airline orders. Consequently, the market struggles to convert high demand into actual revenue efficiently, as the inability to finalize and ship propulsion units directly stalls the ultimate delivery of aircraft to operators.

The severity of this limitation is highlighted by recent industry metrics that show a growing gap between manufacturing goals and actual production. According to the International Air Transport Association (IATA), in 2024, the global commercial aircraft order backlog hit a record peak of nearly 17,000 units, yet actual deliveries missed initial annual forecasts by almost 30% due to these production constraints. This substantial shortfall in deliveries illustrates how supply chain fragility is directly restricting the market's physical expansion, leaving a significant portion of potential market value untapped despite a favorable demand landscape.

Market Trends

The shift toward Ultra-High Bypass Ratio (UHBR) engine designs marks a structural evolution aimed at maximizing propulsive efficiency. Manufacturers are increasingly separating fan speed from the low-pressure turbine through the use of gearboxes, which allows for larger fan diameters and bypass ratios surpassing 15:1. This architectural approach lowers fuel consumption by permitting the fan to rotate more slowly while the turbine functions at optimal speeds. As reported by Flight Global in an October 2025 article titled 'Pratt & Whitney secures European validation for GTF Advantage engine', this advanced UHBR powerplant is engineered to deliver 4% more take-off thrust at sea-level airports and 8% more at high-altitude locations, confirming the performance advantages of geared architectures.

In parallel, the revival of Open Fan concepts seeks to achieve significant reductions in emissions. Unlike traditional ducted turbofans, these configurations eliminate the nacelle to attain bypass ratios double those of existing engines, providing considerable fuel savings. Consortiums are actively advancing these designs into hardware validation stages to demonstrate aerodynamic stability. According to a July 2025 update from CFM International titled '5 Things to Know About the CFM RISE Program', the joint venture has finalized over 250 tests, including wind tunnel campaigns, to refine the open fan architecture for future operational service.

Key Market Players

• RTX Corporation
• General Electric Company
• Rolls-Royce plc
• MTU Aero Engines AG
• Honeywell International Inc.
• Eurojet Turbo GmbH
• Safran SA
• IHI Corporation

Report Scope

In this report, the Global Aircraft Turbofan Engine Market has been segmented into the following categories, in addition to the industry trends which have also been detailed below:

Aircraft Turbofan Engine Market, By Turbofan Engine

• PW1000
• F414
• V2500
• PW4000
• CFM56
• CFM LeapX
• GP7000
• GEnx
• Trent 1000
• F135

Aircraft Turbofan Engine Market, By Aircraft Type

• Wide Body
• Narrow Body
• Others

Aircraft Turbofan Engine Market, By Application Type

• Military Aviation
• Commercial Air Transport

Aircraft Turbofan Engine Market, By Region

• North America
  • United States
  • Canada
  • Mexico
• Europe
  • France
  • United Kingdom
  • Italy
  • Germany
  • Spain
• Asia Pacific
  • China
  • India
  • Japan
  • Australia
  • South Korea
• South America
  • Brazil
  • Argentina
  • Colombia
• Middle East & Africa
  • South Africa
  • Saudi Arabia
  • UAE

Competitive Landscape

Company Profiles: Detailed analysis of the major companies present in the Global Aircraft Turbofan Engine Market.

Available Customizations:

Global Aircraft Turbofan Engine Market report with the given market data, TechSci Research offers customizations according to a company's specific needs. The following customization options are available for the report:

Company Information

• Detailed analysis and profiling of additional market players (up to five).

Table of Contents

1. Product Overview

• 1.1. Market Definition
• 1.2. Scope of the Market
  • 1.2.1. Markets Covered
  • 1.2.2. Years Considered for Study
  • 1.2.3. Key Market Segmentations

2. Research Methodology

• 2.1. Objective of the Study
• 2.2. Baseline Methodology
• 2.3. Key Industry Partners
• 2.4. Major Association and Secondary Sources
• 2.5. Forecasting Methodology
• 2.6. Data Triangulation & Validation
• 2.7. Assumptions and Limitations

3. Executive Summary

• 3.1. Overview of the Market
• 3.2. Overview of Key Market Segmentations
• 3.3. Overview of Key Market Players
• 3.4. Overview of Key Regions/Countries
• 3.5. Overview of Market Drivers, Challenges, Trends

4. Voice of Customer

5. Global Aircraft Turbofan Engine Market Outlook

• 5.1. Market Size & Forecast
  • 5.1.1. By Value
• 5.2. Market Share & Forecast
  • 5.2.1. By Turbofan Engine (PW1000, F414, V2500, PW4000, CFM56, CFM LeapX, GP7000, GEnx, Trent 1000, F135)
  • 5.2.2. By Aircraft Type (Wide Body, Narrow Body, Others)
  • 5.2.3. By Application Type (Military Aviation, Commercial Air Transport)
  • 5.2.4. By Region
  • 5.2.5. By Company (2025)
• 5.3. Market Map

6. North America Aircraft Turbofan Engine Market Outlook

• 6.1. Market Size & Forecast
  • 6.1.1. By Value
• 6.2. Market Share & Forecast
  • 6.2.1. By Turbofan Engine
  • 6.2.2. By Aircraft Type
  • 6.2.3. By Application Type
  • 6.2.4. By Country
• 6.3. North America: Country Analysis
  • 6.3.1. United States Aircraft Turbofan Engine Market Outlook
    • 6.3.1.1. Market Size & Forecast
      • 6.3.1.1.1. By Value
    • 6.3.1.2. Market Share & Forecast
      • 6.3.1.2.1. By Turbofan Engine
      • 6.3.1.2.2. By Aircraft Type
      • 6.3.1.2.3. By Application Type
  • 6.3.2. Canada Aircraft Turbofan Engine Market Outlook
    • 6.3.2.1. Market Size & Forecast
      • 6.3.2.1.1. By Value
    • 6.3.2.2. Market Share & Forecast
      • 6.3.2.2.1. By Turbofan Engine
      • 6.3.2.2.2. By Aircraft Type
      • 6.3.2.2.3. By Application Type
  • 6.3.3. Mexico Aircraft Turbofan Engine Market Outlook
    • 6.3.3.1. Market Size & Forecast
      • 6.3.3.1.1. By Value
    • 6.3.3.2. Market Share & Forecast
      • 6.3.3.2.1. By Turbofan Engine
      • 6.3.3.2.2. By Aircraft Type
      • 6.3.3.2.3. By Application Type

7. Europe Aircraft Turbofan Engine Market Outlook

• 7.1. Market Size & Forecast
  • 7.1.1. By Value
• 7.2. Market Share & Forecast
  • 7.2.1. By Turbofan Engine
  • 7.2.2. By Aircraft Type
  • 7.2.3. By Application Type
  • 7.2.4. By Country
• 7.3. Europe: Country Analysis
  • 7.3.1. Germany Aircraft Turbofan Engine Market Outlook
    • 7.3.1.1. Market Size & Forecast
      • 7.3.1.1.1. By Value
    • 7.3.1.2. Market Share & Forecast
      • 7.3.1.2.1. By Turbofan Engine
      • 7.3.1.2.2. By Aircraft Type
      • 7.3.1.2.3. By Application Type
  • 7.3.2. France Aircraft Turbofan Engine Market Outlook
    • 7.3.2.1. Market Size & Forecast
      • 7.3.2.1.1. By Value
    • 7.3.2.2. Market Share & Forecast
      • 7.3.2.2.1. By Turbofan Engine
      • 7.3.2.2.2. By Aircraft Type
      • 7.3.2.2.3. By Application Type
  • 7.3.3. United Kingdom Aircraft Turbofan Engine Market Outlook
    • 7.3.3.1. Market Size & Forecast
      • 7.3.3.1.1. By Value
    • 7.3.3.2. Market Share & Forecast
      • 7.3.3.2.1. By Turbofan Engine
      • 7.3.3.2.2. By Aircraft Type
      • 7.3.3.2.3. By Application Type
  • 7.3.4. Italy Aircraft Turbofan Engine Market Outlook
    • 7.3.4.1. Market Size & Forecast
      • 7.3.4.1.1. By Value
    • 7.3.4.2. Market Share & Forecast
      • 7.3.4.2.1. By Turbofan Engine
      • 7.3.4.2.2. By Aircraft Type
      • 7.3.4.2.3. By Application Type
  • 7.3.5. Spain Aircraft Turbofan Engine Market Outlook
    • 7.3.5.1. Market Size & Forecast
      • 7.3.5.1.1. By Value
    • 7.3.5.2. Market Share & Forecast
      • 7.3.5.2.1. By Turbofan Engine
      • 7.3.5.2.2. By Aircraft Type
      • 7.3.5.2.3. By Application Type

8. Asia Pacific Aircraft Turbofan Engine Market Outlook

• 8.1. Market Size & Forecast
  • 8.1.1. By Value
• 8.2. Market Share & Forecast
  • 8.2.1. By Turbofan Engine
  • 8.2.2. By Aircraft Type
  • 8.2.3. By Application Type
  • 8.2.4. By Country
• 8.3. Asia Pacific: Country Analysis
  • 8.3.1. China Aircraft Turbofan Engine Market Outlook
    • 8.3.1.1. Market Size & Forecast
      • 8.3.1.1.1. By Value
    • 8.3.1.2. Market Share & Forecast
      • 8.3.1.2.1. By Turbofan Engine
      • 8.3.1.2.2. By Aircraft Type
      • 8.3.1.2.3. By Application Type
  • 8.3.2. India Aircraft Turbofan Engine Market Outlook
    • 8.3.2.1. Market Size & Forecast
      • 8.3.2.1.1. By Value
    • 8.3.2.2. Market Share & Forecast
      • 8.3.2.2.1. By Turbofan Engine
      • 8.3.2.2.2. By Aircraft Type
      • 8.3.2.2.3. By Application Type
  • 8.3.3. Japan Aircraft Turbofan Engine Market Outlook
    • 8.3.3.1. Market Size & Forecast
      • 8.3.3.1.1. By Value
    • 8.3.3.2. Market Share & Forecast
      • 8.3.3.2.1. By Turbofan Engine
      • 8.3.3.2.2. By Aircraft Type
      • 8.3.3.2.3. By Application Type
  • 8.3.4. South Korea Aircraft Turbofan Engine Market Outlook
    • 8.3.4.1. Market Size & Forecast
      • 8.3.4.1.1. By Value
    • 8.3.4.2. Market Share & Forecast
      • 8.3.4.2.1. By Turbofan Engine
      • 8.3.4.2.2. By Aircraft Type
      • 8.3.4.2.3. By Application Type
  • 8.3.5. Australia Aircraft Turbofan Engine Market Outlook
    • 8.3.5.1. Market Size & Forecast
      • 8.3.5.1.1. By Value
    • 8.3.5.2. Market Share & Forecast
      • 8.3.5.2.1. By Turbofan Engine
      • 8.3.5.2.2. By Aircraft Type
      • 8.3.5.2.3. By Application Type

9. Middle East & Africa Aircraft Turbofan Engine Market Outlook

• 9.1. Market Size & Forecast
  • 9.1.1. By Value
• 9.2. Market Share & Forecast
  • 9.2.1. By Turbofan Engine
  • 9.2.2. By Aircraft Type
  • 9.2.3. By Application Type
  • 9.2.4. By Country
• 9.3. Middle East & Africa: Country Analysis
  • 9.3.1. Saudi Arabia Aircraft Turbofan Engine Market Outlook
    • 9.3.1.1. Market Size & Forecast
      • 9.3.1.1.1. By Value
    • 9.3.1.2. Market Share & Forecast
      • 9.3.1.2.1. By Turbofan Engine
      • 9.3.1.2.2. By Aircraft Type
      • 9.3.1.2.3. By Application Type
  • 9.3.2. UAE Aircraft Turbofan Engine Market Outlook
    • 9.3.2.1. Market Size & Forecast
      • 9.3.2.1.1. By Value
    • 9.3.2.2. Market Share & Forecast
      • 9.3.2.2.1. By Turbofan Engine
      • 9.3.2.2.2. By Aircraft Type
      • 9.3.2.2.3. By Application Type
  • 9.3.3. South Africa Aircraft Turbofan Engine Market Outlook
    • 9.3.3.1. Market Size & Forecast
      • 9.3.3.1.1. By Value
    • 9.3.3.2. Market Share & Forecast
      • 9.3.3.2.1. By Turbofan Engine
      • 9.3.3.2.2. By Aircraft Type
      • 9.3.3.2.3. By Application Type

10. South America Aircraft Turbofan Engine Market Outlook

• 10.1. Market Size & Forecast
  • 10.1.1. By Value
• 10.2. Market Share & Forecast
  • 10.2.1. By Turbofan Engine
  • 10.2.2. By Aircraft Type
  • 10.2.3. By Application Type
  • 10.2.4. By Country
• 10.3. South America: Country Analysis
  • 10.3.1. Brazil Aircraft Turbofan Engine Market Outlook
    • 10.3.1.1. Market Size & Forecast
      • 10.3.1.1.1. By Value
    • 10.3.1.2. Market Share & Forecast
      • 10.3.1.2.1. By Turbofan Engine
      • 10.3.1.2.2. By Aircraft Type
      • 10.3.1.2.3. By Application Type
  • 10.3.2. Colombia Aircraft Turbofan Engine Market Outlook
    • 10.3.2.1. Market Size & Forecast
      • 10.3.2.1.1. By Value
    • 10.3.2.2. Market Share & Forecast
      • 10.3.2.2.1. By Turbofan Engine
      • 10.3.2.2.2. By Aircraft Type
      • 10.3.2.2.3. By Application Type
  • 10.3.3. Argentina Aircraft Turbofan Engine Market Outlook
    • 10.3.3.1. Market Size & Forecast
      • 10.3.3.1.1. By Value
    • 10.3.3.2. Market Share & Forecast
      • 10.3.3.2.1. By Turbofan Engine
      • 10.3.3.2.2. By Aircraft Type
      • 10.3.3.2.3. By Application Type

11. Market Dynamics

• 11.1. Drivers
• 11.2. Challenges

12. Market Trends & Developments

• 12.1. Merger & Acquisition (If Any)
• 12.2. Product Launches (If Any)
• 12.3. Recent Developments

13. Global Aircraft Turbofan Engine Market: SWOT Analysis

14. Porter's Five Forces Analysis

• 14.1. Competition in the Industry
• 14.2. Potential of New Entrants
• 14.3. Power of Suppliers
• 14.4. Power of Customers
• 14.5. Threat of Substitute Products

15. Competitive Landscape

• 15.1. RTX Corporation
  • 15.1.1. Business Overview
  • 15.1.2. Products & Services
  • 15.1.3. Recent Developments
  • 15.1.4. Key Personnel
  • 15.1.5. SWOT Analysis
• 15.2. General Electric Company
• 15.3. Rolls-Royce plc
• 15.4. MTU Aero Engines AG
• 15.5. Honeywell International Inc.
• 15.6. Eurojet Turbo GmbH
• 15.7. Safran SA
• 15.8. IHI Corporation

16. Strategic Recommendations

17. About Us & Disclaimer