"There is a no payroll."

You can't do this for an S Corp. An S corp is required to pay Reasonable Compensation to anyone working for the company.

"Company owner is a Shareholder. The shareholder bills hours and travel costs for services delivered."

Which you would still do here.

"However, the Shareholder wants all the service income to stay in the business. Shareholder does not want anything paid to him personally. Wants all the income to stay in the business bank account."

Let's review:

The "income" from sales stays "in the business" because it shows in the financial data. Whether there is also the money still in the bank, or it got paid out as payroll, or it got paid for Rent and Utilities, doesn't change Gross Income.

"I know I need to debit travel expense and consulting expense accounts but what do I credit?"

Nope. What you are asking is the Sale. You make the sale. You also need to honor if there is a sales tax issue. Then, you would write off the sale, if you don't intend to have the customer pay, after all. There is no Debit-this, Credit-that. There is 100% discounted Sale.

"If I credit a Liability account, then the liability is never going to get cleaned out because Shareholder again does not want any cash payment to himself. So should it be credit to Retained earnings and will that not duplicate revenues?"

You really are overthinking all of this.

Under tax form conditions, you see 1 line for Revenue and 1 line for Allowances/Refunds/Write offs.

An employee that doesn't want to be paid for work, is illegally working. The corporation carries the risk of that person performing that work, and the legal requirement to Pay for the work, using Payroll.

Let's try another discussion example:

I run a landscaping company. You work for me. It is an S Corp.

We decide to take some equipment over to a City Park to help make a handicap accessible path. We have normal operating costs, including payroll for you and me. We can not Charge for that sale; or we can Make it and Discount it, which is what you do for a Charity to be able to have proof of Public Support. Or, you and I can do this on weekend, personally, but now the Corporation is at risk; if we roll flat someone's dog or child, the corporation is on the hook.

And don't confuse Gross Revenue or Full Price with donation or contribution. Another example discussion:

You are my employee and I send you to do some work on your own. I have Payroll Cost. The Sales is not a contribution. The Cost would be, but it's already part of my business expense. You don't get to double-dip it.

Even personally, the IRS tells you there is no Cost for Time. If you go mow the yard at the church, you have some value or worth to your time, since you are a professional landscaper, but you just volunteered to mow. There is no Value on your time, here.

Otherwise, what's to prevent you from deciding your tax deduction for contribution  is worth $500 an hour? You can't make up something. It has to have been Incurred.