中文摘要：

根据国家标准GB1105 1-87《内燃机台架性能试验方法标准环境状况及功率、燃油消耗率和机油消耗率的规定》中的等过量空气法,结合内燃机典型变工况解析式及单压过热蒸汽余热锅炉变工况解析解,研究大气条件变化时,系统变工况性能。结果表明,大气压力p_0减小,内燃机相对输出功率（？）减小,相对燃油消耗率（？）增加,系统总能利用率Z减小,当量（？）效率η_（ex）、相对节能率FESR、经济（？）效率θ先增加后减小,存在最大值,在80 kPa左右取得最大值。大气温度t_O升高,（？）减小,（？）增加,Z、η_（ex）、FESR、θ增加。

英文摘要：

According to the national standard GB1105.1-87,Performance Test Methods for Reciprocating Internal Combustion Engine-Standard Ambient Conditions and Declarations of Power, Fuel Consumption and Lubricating Oil Consumption,combined with the typical off-design analysis formula of internal combustion engines and analytical off-design performances of heat recovery steam generator（HRSG）,the law of excess air was applied in this article.When ambient conditions are changed,the off-designed performance of cogeneration system has been investigated. With decreasing of ambient pressure,the relative power output of internal combustion engine P_e and total energy efficiency Z decreased,relative fuel consumption b_e increased,equivalent exergy efficiencyη_（ex）,economic exergy efficiencyθand fuel energy saving-ratio FESR increased first and then decreased,they existed maximal value when the atmospheric pressure was about 80 kPa. With increasing of ambient temperature,the relative power output of internal combustion engine P_e decreased,relative fuel consumption b_e increased,total energy efficiency Z,equivalent exergy efficiencyη_（ex）,economic exergyθefficiency and fuel energy saving-ratio FESR increased to some extent.