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nb89
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I have a P-V trace for a wide open throttle and a part load. Is it possible to calculate the BMEP from these graphs?
How to calculate BMEP from P-V Graphs?
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Discussion Overview
The discussion focuses on the calculation of Brake Mean Effective Pressure (BMEP) from pressure-volume (P-V) graphs, particularly in the context of engine performance analysis. Participants explore various methods and considerations for deriving BMEP from given P-V data, including integration techniques and numerical methods.
Discussion Character
- Technical explanation
- Mathematical reasoning
- Debate/contested
Main Points Raised
- One participant inquires about the feasibility of calculating BMEP from P-V traces for wide open throttle and part load conditions.
- Another participant provides a formula for BMEP based on horsepower, displacement, and RPM, but this is challenged due to the lack of direct values from the P-V data.
- A suggestion is made to integrate the pressure-volume data (PdV) to determine work done, which can then be used to calculate power over a cycle.
- It is proposed that integrating the area under the P-V curve yields the Indicated Mean Effective Pressure (IMEP), which is related to BMEP.
- Participants discuss practical methods for integration, including using software for numerical integration or manual methods such as a planimeter.
- One participant expresses regret for not considering numerical integration in Excel, acknowledging it as a straightforward approach.
Areas of Agreement / Disagreement
Participants generally agree on the need to integrate P-V data to derive BMEP, but there is no consensus on the best method to achieve this or the specific calculations involved. Multiple approaches and tools are suggested, reflecting differing opinions on practicality and effectiveness.
Contextual Notes
Participants mention various assumptions regarding the integration process, such as the need for average pressure values and the specific cycle duration for different engine types. The discussion does not resolve the complexities involved in accurately calculating BMEP from P-V graphs.
Who May Find This Useful
This discussion may be useful for individuals interested in engine performance analysis, particularly those looking to understand the relationship between P-V data and BMEP calculations, as well as those seeking practical integration techniques for engineering applications.