Numerical Investigation of PPCI Combustion at Low and High Charge Stratification Levels

Abstract

The authors need to carefully proofread their manuscript for grammatical errors. The articles "a" , "an" and "the" are either missing or unnecessarily inserted throughout the paper. A few examples include: Abstract, 1st sentence:insert "the" before 'low temperature combustion' (also, a note on capitalization-even though the abbreviation is capitalized, the full words are not) Abstract, 3rd sentence:insert "the" between 'lowers' and 'rate of heat release' Introduction, 1st sentence:delete 'been' and insert "a" after 'triggered' (see earlier note on capitalization as it also applies to 'internal combustion') Be sure to double check for spelling errors as well.(Caption for Fig. 8 on p. 7:"startification" should be spelled "stratification", and p. 9 last paragraph "fist" should be spelled "first" and "form" should be spelled "from") Some sentences are confusing and need to be clarified. A few examples include: P. 2 paragraph after Table 1: "Izadi et al. [8] found that ignition sensitivity for the experiments as in Fig. 1."This could be edited many ways, but it seems like the authors meant to insert a clause describing some notable result from [8] before the phrase "as in Fig. 1." P. 9 Second to last sentence in the "SOI-40" paragraph:"This is due to availability of larger amount of fuel in SOI-80 while second stage ignition." Thanks for the detailed observation of Reviewer 1. We have amended the manuscript text accordingly. Overall, this CFD paper helps to explain the experimental results observed in SAE Technical Paper 2016-01-0761. Note that I had to search for this paper number because the references section does not list the paper number for [8]. The authors need to be cautious about making broader, unproven claims that air-fuel mixture stratification can effectively control PPCI combustion phasing "under different engine operating conditions" (last sentence of abstract) when they only investigated a single, low-load operating condition. Abstract was changed. Please check. The authors acknowledge, in the last sentence of the second paragraph of the Introduction, that "There have note the correction from "has" to "have" been a number of experimental and numerical studies on the effect of mixture stratification on note the deletion of unnecessary article "the" PPCI combustion characteristics", so given that they are aware of other relevant papers it would be pertinent and informative to briefly review/compare/contrast (cite!) these works in the Introduction and discussion of their own results. There was a misunderstanding in the first draft. After this sentence both experimental and numerical literature review were provided. Please check.

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