Jewell inherits a Tractor Boys side who have slipped towards the relegation zone and who were knocked out of the FA Cup with a 7-0 humbling at Chelsea on Sunday.
His first game will be the first-leg of a Carling Cup semi-final against Arsenal on Wednesday.
"If you look at the Championship there are a lot of big teams with the same expectation of getting out of this league. It's very tough," he said.
"The owner will support us in the things we want to do but I'm not going to blow everyone out of the water here.
"I want to improve the players we already have here and if there are players who can come in who can improve us we will look to do that."
Simon Clegg, the Ipswich chief executive, pointed to Jewell's record of leading Bradford City and Wigan Athletic to the top flight.
"The owner Marcus Evans and I were sure that Paul's track record - including being one of only three managers to achieve promotion to the Premier League with two different clubs - means he is the right man for the job," he said.
"We as a club need to look forwards and we will fully support him in achieving his objectives."
The chief executive of Norwich City, David McNally, has criticised Burnley for making public their approach for their manager Paul Lambert.
The Clarets made Lambert their first-choice to replace Brian Laws, and released a statement on Thursday evening to that effect.
Norwich refused them permission to speak to Lambert, and he has since described the approach as unwelcome.
"Burnley, for some bizarre and difficult to explain reason, had decided to put on their website that they had asked for permission to speak to Paul about their vacancy," said McNally.
"That really was unusual, unexpected and I have to say unprofessional of them. It meant we had to get something out to say that we would absolutely make certain that Paul Lambert stayed manager of Norwich City and he was certainly not going to Burnley, there was no question of that."
The Nottingham Forest defender Kelvin Wilson has admitted he is not focused on the club, after signing a pre-contract with the Scottish Premier League side Celtic.
Wilson, 25, would be keen to quit the City Ground this month rather than wait until the summer.
"That would definitely suit me because my mind is at Celtic. I would prefer to move to Scotland this month and get on with my career," he told the Nottingham Post.