Normalization of the Indirect Measurement Errors of Acceptance Engine Tests

This article discusses the issues of ensuring the accuracy and reliability of the measurement results of controlled engine parameters during acceptance tests. GOST 18509-88 “Tractor and combine diesel engines. Bench test method” establishes the permissible errors of the main controlled parameters of engines during acceptance tests; however, no requirements hold for the permissible error in engine power measurements. On the basis of probability theory, an equation was derived for calculating power measurement errors, and the permissible measurement errors (according to GOST 18509-88) in the power measurements of overhauled engines of various brands were calculated. A comparative analysis of these calculated results and the actual error in measuring power during running-in on the stands KI-5274, KI-5540M, KI-5541M, KI-542M, and KI-2118A of the Russian Scientific Research Technological Institute for the Repair and Operation of the Machine and Tractor Park of the Russian Agricultural Academy was performed. This comparison established that the power measurement errors exceed the maximum allowable values. Recommendations were developed for calculating acceptance windows with a shift relative to the nominal power value to improve the veracity of power control results. The limiting errors in measuring the power of engines of various brands and acceptance limits were calculated depending on the required reliability. This methodology increases the veracity of control results at the acceptance test stage of an overhauled engine.